Grate



R. c. RlvERs l2,971,508

GRATE 5 Sheets-Sheet 1 INVENTOR. Russell C.. RiUeTs Feb. 14, 1961 Filed Dec. 26, 1957 O ILey Feb. 14, 1961 Filed Deo. 26, 1957 R. C. RIVERS GRATE 3 Sheets-Sheet 2 INVENToR. Russell C. Riz/ers j MY Ji H O'rney UnitedStates PatentO GRATE Russell C. Rivers, Boylston, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Filed Dec. 26, 1957, Ser. No. 705,438

Claims. (Cl. 126-174) t This invention relates to a grate and more particularly to apparatus for use in the burning of solid fuel in a steam generating unit.

It has been suggested that the fuel burning grate in a steam generating unit be mounted resiliently and subjected to vibration in order to move consumed fuel toward one end where it may fall into an ash pit. Such a grate is shown and described in the co-pending patent application of Craig, Serial No. 460,339, tiled October 5, 1954, and now Patent No. 2,848,959. It has` been discovered, however, that certain diiculties arise in connection with a grate of this type. For one thing, a problemis experienced with the manner in which the grate bars are fastened to the grate frame; the constant vibration subjects the usual fasteners to dynamic forces which pennit them to loosen, and, when this takes place, rapid wear and undesirable noise occurs. These and other difficulties with the prior art devices have been obviated in a novel manner by the present invention.

It is therefore an outstanding object of the invention to provide a furnace grate of the vibrating type in which the possibility of grate bars loosening is eliminated.

Another object of this invention is the provision of a vibrating grate of such a construction as to permit better alignment of the grate bars, quicker and easier installation of the grate surface, and improved compensation for thermal expansion. i

A still further object of` this invention is the provision of a grate in which the sifting of ne ash into the Windbox under the grate is considerably reduced.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to certain of its structural forms,

as illustrated by the accompanying drawings in which:

Figurel is a side elevation view, with portions broken away, of a grate of a steam generating unit embodying the principles of the present invention,`

Figure 2 is a plan view of the grate with portions broken away,

Figure 3 is a sectional view of a portion of the grate taken on the line Ill-111 of Figure 4, and

Figure 4 is a sectional view of another portion of the grate.

In this specification, the expressions front and rear and the like, refer to the corresponding directions relative to the movement of fuel and ash along the grate.

Referring rst to Figures l and 2, wherein are best shown the generalfeatures of the invention, the grate, indicated generally by the reference numeral 10, is mounted on a foundation 1-1 which is the foundationof a steam generating unit, the elements of which are not shown. It will be understood, however, that the grate is designed to be installedtin the lowerportion of the combustion chamber of a steam generating unit and that the usual fuel-feeding means is provided on the wall of the 2,971,508 Patented Feb. 14,1961

ICC

combustion chamber overlying the grate in such a manner that fuel is thrown onto the upper surface of the grate. The grate consists generally of a base frame 12 which is bolted to the foundation 11 and an upper frame 13 which carries grate bars 14 and which is joined to the base 12 by means of resilient leaves 15. A motor 16 is connected by a flexible drive belt 17 to a shaft 18 suitably mounted in bearings on the underside of the frame 13. The shaft 18 carries eccentric Weights, not shown, to produce the vibratory impulse necessary to move the grate to and fro.

The frame 13 consists of side members 19' joined by parallel support members 21. These support members are T-shaped structural beams having the arms extending horizontally in the upper portion andthe legs hanging downwardly. The grate bars 14 are elongated and `extend from one support member 21 to another. As is evident in Figure 2, the grate bars are relatively narrow. In order to maintain the drawings relatively uncomplicated, only one grate 14 has been shown in detail in Figures 1 and 2. While the upper surface of the grate 14 is relatively dat and unbroken, the underside is provided with pockets 22 and 23 extending upwardly therein, thus forming the lower part of the grate bar into three ribs 24, 25, and 26. As is evident in Figure l, the recess 23, for instance, extends quite close to the upper surface of the grate so that only a thin web remains and this web is pierced by air holes 27. The forward end of the grate 14is provided on its undersurface with a recess 28 defining a vertical shoulder 29 so that the grate rests on the support members 21 with one arm of the member residing in the recess 28 with the shoulder 29 acting as a stop. At the other, or rearward, end of the grate bar a recess 31 is provided, the horizontal surface of which rests on another support member 21 but which has a shoulder considerably removed from the forward edge of the arm of the support member so that 'the grate bar is to accommodate the leaf 15 at its selected angle.

free to slide in either direction.

Referring next to Figure 3, it can be seen that a coil spring 32 is fastened at one end to an aperture 33 in the central web 25 of the grate bar 14, while the other end is hooked in a similar aperture in an angle iron 34 which is bolted to the support member 21. It should be noted that the `grate bar 14 shown in Figure 3 is `one which resides ladjacent the side of the grate and is located over theportion occupied by the leaves 15. As a matter of fact, the leg of the support member 21 is bent rearwardly In Figure 4 is shown a similar situation wherein the grate bar 14 is one of those which occupies a portion of the grate not occupied by leaves 15. In this case, a spring 35 is engageable with an aperture 36 in the leg of the 4 support member 21.` In Figures 3 and 4 it should be noted also that the corner of the recess 28 which is engaged `by the edge of the arm of the support member 21 is provided with a relief groove which assures that the grate may closely embrace the edge Of the support member. In these figures it can be seen that the forward end of each grate bar 14 is provided with a tongue 38 which engages -a recess 39 in the rearward end of the adjacentgrate bar. A space 41 of considerable dimensions is provided between adjacent grate bars to permit the rearward ends to move to and fro along the sup- 'port member 21 as the grate bar expands and contracts 'l the forward end of the grate is located a vertical abutd the grate and the abutment 44 faces` the ash pit. The

ment 42 consisting of a channel 43, having its recess opening' forwardly, the recess being lled with insulating material 44. This, of course, is the dischargelend of i upperhorizontalsurface of the channel 43 is quite at and resting on this surface is one end of an auxiliary sealing grate bar 45 which is provided with a downwardly depending flange 46 which locks behind a bead 47 welded to the arm of the most rearward supporting member 21 of the upper frame 13. The tongue 38 of the ladjacent grate bar 14 engages a recess 48 in the grate bar 45 which is similar to the recess 39 provided at the rearward end of each of the grate bars 14. This serves to lock the grate bar 45 in place. At the other end of the grate, means is provided to protect the motor 16 and its associated equipment for vibrating the grate. For this purpose, a wall 49 extends upwardly and rearwardly of the motor 16 and is provided at its upper end with a vertical flange 51. A sealing member 52 extends laterally across the grate and is provided with a groove 53 which engages the flange 51 in such a manner that the sealing member rests lightly on the upper surface of the grate and is prevented from moving longitudinally by the engagement between the groove 53 and the ange 51. At this same end of the grate, the frame 13 is provided with a lateral supporting member 54 on which may rest the rearward ends of the end grate bars 14. To a dependent leg of this support memmebr 54 is fastened a horizontal insulating wall 55 which extends under the grate above the motor 16 and its associated equipment. Fastened to the base 12 on the forward side of the motor 16 is `a vertical insulating wall 56 whose upper edge closely underlies the insulating wall 55. The forward edge of the wall 55 and the upper edge of the wall 56 are joined yby a flexible metal connector 57 which renders the junction relatively gas-tight.

The operation of the invention will now be readily understood in view of the 'above description. lDuring the operation of a steam generating unit, solid fuel is thrown onto the upper surface of the grate bars 14. Combustio-n air enters the windbox under the grate and passes upwardly through the air holes 27 i-n the grate and combustion takes place on the surface of the grate.

From time to time it will be desired to move burned fuel to the end of the grate for discharge into the ash pit and for that purpose the motor 16 is operated. The motor drives the belt 17 to rotate the shaft 18 and bring about the vibration of the upper frame 13 and grate bars 14 on the resilient support furnished by the leaves 15. Because of the inclination of the leaves 15 the surface of the gratebars impart more energy to the fuel and ash in the discharge direction than it does in the opposite direction. This causes the fuel and ash to move to the ash pit end of the grate where they fall off into the ash pit. Leakage of gas around the discharge end of the grate is prevented by the contact between the grate bars 45 and the upper surface of the abutment 42. Sifting of Iashes and the like into the area occupied by the motor 16 and the associated equipment is prevented by the frictional cont-act between the sealing members 52 and the upper surfaces of the grate bars in its neighborhood. The space in which the motor and its equipment resides is kept relatively cool by the insulating walls 55 and 56. At the same time there is no leakage of air because of the presence of the exible member 57 which is gas-tight. The insulating wall 55 moves with the supporting member 54 and Ithe rest of the grate in its lvibratory movement. The vertical insulating wall 56 remains fixed, however, and very little movement s permitted by the exible member 57.

Each spring 32 acts to maintain its grate bar 14 in` position at all times. The spring maintains the grate bar in its forward position with the shoulder 29 engaging the edge of the arm of the forward supporting member 21. At the other end of the bar considerable slid.- ing movement is permitted of the grate bar over the surface of `the rearward supporting member 21. This movement will take place during thermal expansion and contraction of the grate bar and, on a long-time basis, Will permit the natural growth of the grate bar due-to grain structure and the like. When it is desired to remove a single grate bar, this may be done from the upper surface of the grate `by inserting a crowbar between the desired grate -and'a closely adjacent grate bar and prying upwardly. Once one end of the grate bar has been lifted against the resistance presented by the spring 32, the grate bar is rotated about a vertical axis and the ends rested on the upper surfaces of the two adjacent grate bars. If there are no adjacent grate bars on which to rest the subject grate bar, the grate bar may be dropped into the space between the supporting members so that the tension in the spring 32 is released and it is possible to remove the spring 32 from the grate bar and the grate bar is then free to be removed entirely from the furnace. Because the spring 32 is under constant tension, the grate bar is maintained in contact with its supporting members and there are no other fastenings to loosen up due to the vibration of the grate.

Furthermore, this type of mounting permits a'better alignment of grate bars, quicker and easier installation of the grate surface, and improved expansion allowance. A marked improvement in the reduction of siftings into `the wind box has also been accomplished. This is in part accomplished by the fact that the grate bars will remain tight on the supporting members. This is further accomplished by the improvement in the method of sealing between the ends of adjacent grate bars. This improved sealing has a secondary but equally important advantage of providing a better air ow pattern through the fuel bed. The grate bars have been designed for excellent air ow control and the reduction of siftings. The particular method o-f constructing the end grate bars 45 and their engagement with the abutment 42 results in improved performance of the grate because there is less restriction and friction to inhibit grate action, yet this is accomplished without the loss of an adequate air seal at this point. Each grate bar has a uniform ribbing throughout its length which provides more uniform lair cooling of the grate bar and more uniform air distribution to and through the grate bar. It is obvious that minor changes may be made in the form and construction of the invention without departing from the matet rial spirit thereof. It is not, however, desired to conline the invention to the exact form herein shown and 1. A furnace grate of the type constructed to movev burned fuel to one end of the grate for discharge into an ash pit, comprising a frame having parallel, spaced, horlzontal support members extending laterally of the grate, elongated grate bars extending longitudinally of the grate, each grate bar having each of its ends resting on one of said support members, and a coil spring placed in tension by attachment at one end to the underside of each of said grate bars near the end of said bars thereof more closely adjacent thev discharge end of the grate and at lthe other end to the lower part of one of the support members on which the grate bars rest, the spring constitutingy substantially the sole fastening existing between the grate bar and the support member, the underside of each of said gratesbars being formed with a stop which engages the supporting member to which said spring is attached to limit movement in the direction of the discharge end of the grate.

2. A fuel-burning grate consisting of a frame having parallel, spaced, horizontal support members, an elongated grate bar having each of its ends resting on a support member, a tension spring attached at one end to the under side of said grate bar and at the other end to the lower part of one of the support members on which the grate bar rests, and stop means on said grate bar adjacent to and engageable with said one support member to limit lengthwise movement of said grate bar relative to Said support members.

3. A fuel-burning grate consisting of a frame having parallel, spaced, horizontalsupport members, an elongated grate bar having each of its ends resting on a support member, a tension spring attached at one end to the under side of the grate bar and at the other end to the lower part of one of the support members on which the -grate bar rests, the spring constituting substantially the sole fastening existing between the grate bar and support member, and stop means on said grate bar adjacent to and engageable with said one support member to limit lengthwise movement of said grate bar relative to said support members.

4. A fuel-burning grate consisting of a frame having parallel, spaced, horizontal support members extending laterally of the grate, an elongated grate bar having each of its ends resting on a support member, a coil spring placed in tension by attachment at one end to the under side of said grate bar and at the other end to the lower part of one of the support members, the spring constituting substantially the sole fastening existing between the grate bar and the support member, and stop means on said grate bar adjacent to and engageable with said one support member to limit lengthwise movement of said grate bar relative to said support members.

5. A furnace grate of the type constructed to vibrate 25 horizontal support members extending laterally of the grate, elongated grate bars extending longitudinally of the grate. each grate bar having a at upper surface and a plurality of downwardly-extending ribs extending 1ongitudinally thereof, air holes extending vertically through each bar between pairs of the ribs, each grate bar having each of its ends resting on one of said support members, each of said grate bars being provided with a coil spring placed in tension by attachment at one end of the under side of the grate bar at the end thereof closely adjacent the discharge end of the grate and at the other end to the lower part of one of the support members on which the grate bar rests, the spring constituting substantially the sole fastening existing between the grate bar and the support member, the under side of each grate bar being formed with a stop which engages the supporting member to which its spring is attached to limit movement in the direction of the discharge end of the grate.

References Cited in the le of this patent UNITED STATES PATENTS 1,534,380 Hancock Apr. 21, 1925 1,939,177 LOsch Dec. l2, 1933 2,499,735 Ellis Mar. 7, 1950 FOREIGN PATENTS 68,629 Switzerland May 18, 1914 

